Most poisons are lethal to the body, yet a small group of venoms influence the mind, destroying free will. Administered regularly, such substances render their subjects susceptible to the influence and suggestions of those closest to them, making them appear as if they had no will of their own. Yet these poisons are very difficult to concoct, for they require very rare ingredients. In addition, their creator must summon the Power in quantities far beyond those available to the everyday village witch. Impotence is caused by poisons of yet another variety, used chiefly by court plotters seeking to control the fate of dynasties and noble houses. These poisons must be administered in very small doses, as in excess amounts they can topple a horse. The worst of all are delayed-action venoms. Poisons of this kind may kill many years after being consumed, years during which the victim's health declines, though no sound medical reason for this can be found.